This invention relates to a temperature control system for instruments which provide cyclic tests on metallic samples resulting in mechanical strain data, and more particularly to a temperature control system for varying the temperature of the sample during the test to provide conditions more similar to the actual process.
Existing instruments provide mechanical strain data on metallic samples to determine the number of cycles that a sample is capable of withstanding the mechanical load. This information is useful in designing various process equipment. However, in some instances, the variation in strain which occurs in the equipment is associated with a change in temperature. Normally thermal cycling reduces the ability of the sample to withstand the same number of cycles compared to those at a fixed temperature. Accordingly, modification of existing instruments is desirable to represent actual conditions.
Therefore, one object of the invention is a temperature control system for varying the temperature (.DELTA.t) of the sample with increasing strain (.DELTA.s) in a fully reversed strain cycle test. A second object is a temperature control system for adjusting the average test temperature prior to the test and changing the .DELTA.t/.DELTA.s to provide a predetermined maximum test temperature. Another object is a temperature control system for providing a low cost circuit to accomplish the above objects.